Gastroesophageal reflux occurs when stomach acid enters the esophagus. This reflux of acid into the esophagus occurs naturally in healthy individuals, but also may become a pathological condition in others. Effects from gastroesophageal reflux range from mild to severe. Mild effects include heartburn, a burning sensation experienced behind the breastbone. More severe effects include a variety of complications, such as esophageal erosion, esophageal ulcers, esophageal stricture, abnormal epithelium (e.g., Barrett's esophagus), esophageal cancer, and/or pulmonary aspiration. These various clinical conditions and changes in tissue structure that result from reflux of stomach acid into the esophagus are referred to generally as Gastroesophageal Reflux Disease (GERD).
Many mechanisms contribute to prevent gastroesophageal reflux in healthy individuals. One such mechanism is the functioning of the lower esophageal sphincter (LES). With reference to FIG. 1, the LES is a region of smooth muscle and increased annular thickness existing in the last four centimeters of the esophagus. In its resting state, the LES creates a region of high pressure (approximately 15-30 mm Hg above intragastric pressure) at the opening of the esophagus into the stomach. This pressure essentially closes the esophagus so that contents of the stomach cannot pass back into the esophagus. The LES opens in response to swallowing and peristaltic motion in the esophagus, allowing food to pass into the stomach. After opening, however, a properly functioning LES should return to the resting, or closed state. Transient relaxations of the LES do occur in healthy individuals, however, typically resulting in normal physiological functions such as belching and vomiting.
The physical interaction occurring between the gastric fundus and the esophagus also prevents gastroesophageal reflux. The gastric fundus is a lobe of the stomach situated at the top of the stomach proximal to the esophagus. In healthy individuals, the fundus presses against the opening of the esophagus when the stomach is full of food and/or gas. This effectively closes off the esophageal opening to the stomach and helps to prevent acid reflux back into the esophagus.
In individuals with GERD, the LES functions abnormally, either due to an increase in transient LES relaxations, decreased muscle tone of the LES during resting, or an inability of the esophageal tissue to resist injury or repair itself after injury. More generally, GERD results from a change in the geometrical relationship between the esophagus and the fundus of the stomach. Normally, the fundus extends above the exit of the esophagus into the stomach. Thus, as intra-abdominal pressure increases, the fundus pushes against the LES to assist in closing the LES. In people with GERD, the fundus flattens out so that it no longer assists in closing the fundus. Moreover, the LES tends to shorten from about 4 cm to about 2 cm in length. GERD can also be caused by hiatel hernia, which also may potentially lead to a change in the geometric relationship as described above. These conditions often are exacerbated by overeating, intake of caffeine, chocolate or fatty foods, and/or smoking. Avoiding these exacerbating mechanisms helps reduce the negative side effects associated with GERD, but does not cure the disease completely.
A surgical procedure, known generally as fundoplication, has been developed to prevent acid reflux in patients whose normal LES functioning has been impaired. Fundoplication involves bringing the fundus into closer proximity to the esophagus to help close off the esophageal opening into the stomach. In Nissen Fundoplication, a particular type of the fundoplication procedure, the fundus is pulled up and around the esophagus and sutured both to itself and to the esophagus such that it completely encircles the esophagus. Traditionally, this procedure has been performed as an open surgery, but has recently enjoyed success as a laparoscopic procedure, as discussed in McKernan, J. B., Champion, J. K., “Laparoscopic antireflex surgery,” American Surgeon, Vol. 61, pp. 530-536, (1995).
As with any open surgery, the risks attendant in such a procedure are great. Due to relatively large incisions necessary in the performance of open surgery, relatively large amounts of blood are lost and risk of infection increases. Though laparoscopic surgical procedures reduce these negative effects by using relatively small devices at a relatively small incision site in the abdominal wall, there still exists an increased risk of infection due to the incision. The location of the incision in the abdominal wall presents a risk of other negative effects, such as sepsis, which can be caused by leakage of septic fluid contained in the stomach. Furthermore, as with any surgery, there exists a small risk of morbidity and mortality associated with the use of general anasthesia.